During the next five years studies will focus on the enzymology of dehalogenation and the enzymology of phosphorus-carbon bond formation and cleavage. These investigations are aimed at discovering, exploring and developing novel enzyme catalysts. The six specific aims of this project are: (1) to determine the substrate specificities and mechanisms of action of the enzymes of the 4-chlorobenzoate to the 4-hydroxybenzoate pathway of pseudomonas sp. CBS-3; (2) to engineer the pseudomonas sp. CBS-3 4-chlorobenzoate-CoA dehalogenase, (3) to determine the mechanism of P-C bond formation catalyzed by PEp mutase; (4) to determine the mechanism of action of the P-C bond cleaving enzymes phosphonoacetaldehyde hydrolase and phosphonoacetate hydrolase; (5) to determine the mode of P-C bond formation in the biosynthesis of phosphonotyrosine, and (6) to purify and characterize the phosphonopyruvate -ketodecarboxylase and 2-aminoethyl phosphonate transaminase of the 2-aminoethylphosphonate pathway.